The present invention relates to integrated circuit arrangements and, more particularly, to the attachment of a heat sink to an integrated circuit die.
Integrated circuit devices mounted to integrated circuit package boards generate large amounts of heat when operated. The generated heat must be dissipated, otherwise the life of the circuit devices will be shortened and the effectiveness of the circuit devices degraded.
A common arrangement for dissipating heat is to utilize a thermally conductive lid that covers and protects a circuit device. Sometimes the increased surface area of the lid is not enough to dissipate sufficient quantities of heat, so a heat sink is mounted to the lid to enhance heat dissipation. Adding a lid to an integrated circuit arrangement, however, increases the cost of the arrangement and increases manufacturing complexity. Therefore, many integrated circuit arrangements do not include a lid for covering and protecting a circuit device, but there remains a need to dissipate excess heat generated by circuit devices.
Accordingly, another common arrangement for dissipating heat is to utilize a heat sink mounted directly onto a circuit device. Heat sinks are manually mounted directly to the circuit device to thermally couple the circuit device and the heat sink. Typically, a heat sink is constructed from highly thermally conductive materials and is exposed to the ambient air or to air moved by some type of cooling fan. The heat sink, thermally coupled to the integrated circuit device, draws heat from the circuit device through conduction. The ambient air, or air moved by the cooling fan, passes over the heat sink to cool the heat sink by convection. As a result, the heat generated by the circuit device is dissipated to the surrounding air.
There are problems related to manually mounting a heat sink directly to a circuit device. Some of these problems relate to the fact that the surface area of a heat sink is large compared to the surface area of a circuit device. It is difficult to properly align a heat sink on top of a circuit device because a person manually mounting the heat sink cannot easily see the circuit device. The relatively small surface area of a circuit device also makes it easy to mount the heat sink at an angle, so that the plane formed by the bottom of the heat sink is not parallel with the plane formed by the top of the circuit device.
Improper alignment of a heat sink on a circuit device leads to inefficient use of the heat sink. An efficient placement for a heat sink is centering the heat sink on the circuit device. Centering the heat sink on the circuit device provides even dissipation of heat generated by the device throughout the entire heat sink. When the heat sink is not properly centered, some portions of the heat sink become hotter than other portions, resulting in uneven and slower heat dissipation from the device to the heat sink. As a result of the uneven dissipation of generated heat, the circuit device may overheat and become damaged, thereby degrading the device""s performance and shortening its operational life.
In addition to mis-centering, a poor thermal interface between the heat sink and the circuit device may occur when the heat sink is not flatly mounted, i.e., the plane formed by the underside of the heat sink is not parallel with the plane formed by the top of the circuit device. An optimal thermal interface occurs when the heat sink is flatly mounted onto the circuit device so that the heat sink is as close as possible to the circuit device, and there is a minimum amount of adhesive between the circuit device and the heat sink. However, when a heat sink is manually mounted onto a circuit device it is easy to improperly mount the heat sink at an angle, instead of flatly on the circuit device. An angle between the heat sink and the circuit device means that a portion of the heat sink is unnecessarily located away from the circuit device, and there will be greater quantities of adhesive between the heat sink and the circuit device, resulting in a poor thermal interface. A poor thermal interface reduces conduction between the device and the heat sink, thereby reducing the heat sink""s ability to dissipate heat generated by the circuit device. This creates the possibility that the circuit device will overheat and become damaged which degrades the device""s performance and shortens its operational life.
Even when a heat sink is properly centered and flatly mounted on a circuit device, several problems can arise. Too much pressure on an edge of a heat sink when connecting an integrated circuit package to a motherboard, for example, creates a force strong enough to tilt or disconnect the heat sink from the circuit device. Rocking of the heat sink, if the integrated circuit package is part of a laptop computer or the electronics in a vehicle for example, could also occur. Rocking of a heat sink on a circuit device results in the device becoming chipped or the heat sink losing optimal thermal contact with the device, either of which detrimentally affects the performance of the device and its operational life.
There is a need for a heat sink mounting that reduces the tilting of a heat sink during installation and operation of the electronic unit in which an integrated circuit arrangement is incorporated, that reduces the risk of damage to the integrated circuit die, and that allows flat thermal contact between the die and the heat sink.
These and other needs are met by embodiments of the present invention which provide a spring-like structure substantially surrounding a die and partially supporting a heat sink.
Accordingly, one aspect of the invention provides a cool spring frame comprising a metal frame having two bends about which the frame flexes, wherein the bends are adapted to be attached to a package board surface. A central opening in the center of the metal frame allows the frame to surround an integrated circuit die mounted on the package board surface.
Accordingly, another aspect of the invention provides a compliant structure comprising polymer components substantially surrounding an integrated circuit die. The height of the compliant structure is greater than the height of the die, and the compliant structure is compressed when a heat sink is mounted to the die, preventing the heat sink from tilting during or after attachment.
The use of a spring-like structure to mount the heat sink to the integrated circuit die and to the package face promotes flat thermal contact between the heat sink and the circuit die. The spring-like structure prevents the heat sink from tilting during installation and operation of the integrated circuit arrangement and prevents damage to the die during heat sink installation and removal. The spring-like structure also reduces the heat sink attachment force on the backside of the integrated circuit die.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.